import sys
import pygame
from bullet import Bullet
from alien import Alien
from time import sleep

def check_keydown_event(event, ai_settings, screen, ship, bullets):
	"""响应按键"""
	if event.key == pygame.K_RIGHT:
		ship.moving_right = True
	if event.key == pygame.K_LEFT:
		ship.moving_left = True
	if event.key == pygame.K_SPACE:
		fire_bullet(ai_settings, screen, ship, bullets)
		
		
def fire_bullet(ai_settings, screen, ship, bullets):
	"""如果还没有达到限制，就发射一颗子弹"""
	if len(bullets) < ai_settings.bullet_allowed:
		new_bullet = Bullet(ai_settings, screen, ship)
		bullets.add(new_bullet)
		
		
def check_keyup_event(event, ship):
	"""响应松开"""
	if event.key == pygame.K_RIGHT:
		ship.moving_right = False
	if event.key == pygame.K_LEFT:
		ship.moving_left = False		

def check_events(ai_settings, screen, ship, bullets):
	"""响应按键和鼠标事件"""
	for event in pygame.event.get():
		if event.type == pygame.QUIT:
			sys.exit()
			
		elif event.type == pygame.KEYDOWN:
			check_keydown_event(event, ai_settings, screen, ship, bullets)
				
				
		elif event.type == pygame.KEYUP:
			check_keyup_event(event, ship)
			
def update_screen(ai_settings, screen, ship, aliens, bullets):
	"""更新屏幕上的图像，并切换到新屏幕"""
	
	# 每次循环时都重绘屏幕
	screen.fill(ai_settings.bg_color)
	
	
	# 在飞船和外星人后重绘所有子弹
	for bullet in bullets.sprites():
		bullet.draw_bullet()
		
	ship.blitme()
	# alien.blitme()
	aliens.draw(screen)
	
	# 让最近绘制的屏幕可见
	pygame.display.flip()
	
def update_bullets(ai_settings, screen, ship, aliens, bullets):
	"""更新子弹位置，并删除已经消失的子弹"""
	# 更新子弹位置
	bullets.update()
	
	# 删除已经消失的子弹
	for bullet in bullets.copy():
		if bullet.rect.bottom <= 0:
			bullets.remove(bullet)
	# print(len(bullets))
	check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets)
		
def check_bullet_alien_collisions(ai_settings, screen, ship, aliens, bullets):
	"""响应子弹和外星人的碰撞"""
	# 检查是否有子弹击中了外星人
	# 如果是这样，就删除相应的子弹和外星人
	collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
	
	if len(aliens) == 0:
		# 删除现有的子弹并新建一群外星人
		bullets.empty()
		create_fleet(ai_settings, screen, ship, aliens)
	
	
	
def get_number_aliens_x(ai_settings, alien_width):
	"""计算每行可以容纳多少个外星人"""
	available_space_x = ai_settings.screen_width - 2 * alien_width
	number_aliens_x = int(available_space_x / (2 * alien_width))
	return number_aliens_x
	
	
def create_alien(ai_settings, screen, aliens, alien_number, row_number):
	"""创建一个外星人并放在当前行"""
	alien = Alien(ai_settings, screen)
	alien_width = alien.rect.width
	alien.x = alien_width + 2 * alien_width * alien_number
	alien.rect.x = alien.x
	alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
	aliens.add(alien)
	
	
def create_fleet(ai_settings, screen, ship, aliens):
	"""创建外星人群"""
	alien = Alien(ai_settings, screen)
	number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
	number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)
	
	# 创建外星人群
	for row_number in range(number_rows):
		for alien_number in range(number_aliens_x):
			create_alien(ai_settings, screen, aliens, alien_number, row_number)
		
def get_number_rows(ai_settings, ship_height, alien_height):
	"""计算屏幕可以容纳多少外星人"""
	available_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
	number_rows = int(available_space_y / (2 * alien_height))
	return number_rows
	
def update_aliens(ai_settings, stats, screen, ship, aliens, bullets):
	"""检查是否有外星人位于屏幕边缘，并更新外星人群中所有外星人的位置"""
	check_fleet_edges(ai_settings, aliens)
	aliens.update()
	
	# 检测外星人和飞船之间的碰撞
	if pygame.sprite.spritecollideany(ship, aliens):
		print("Ship hit!!!")
		
	# 检测外星人和飞船碰撞
	if pygame.sprite.spritecollideany(ship, aliens):
		ship_hit(ai_settings, stats, screen, ship, aliens, bullets)
		
	# 检查是否有外星人到达屏幕底端
	check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets)
	
def check_fleet_edges(ai_settings, aliens):
	"""有外星人达到边缘时采取相应的措施"""
	for alien in aliens.sprites():
		if alien.check_edges():
			change_fleet_dirction(ai_settings, aliens)
			break
			
def change_fleet_dirction(ai_settings, aliens):
	"""将整群外星人向下移动，并改变它们的方向"""
	for alien in aliens.sprites():
		alien.rect.y += ai_settings.fleet_drop_speed
	ai_settings.fleet_direction *= -1
	
def ship_hit(ai_settings, stats, screen, ship, aliens, bullets):
	"""响应被外星人撞到的飞船"""
	
	# 将ships_left 减一
	stats.ships_left -= 1
	
	# 清空外星人列表和子弹列表
	aliens.empty()
	bullets.empty()
	
	# 创建一群新的外星人，并将飞船放到屏幕低端中央
	create_fleet(ai_settings, screen, ship, aliens)
	ship.center_ship()
	
	# 暂停
	sleep(0.5)
	
def check_aliens_bottom(ai_settings, stats, screen, ship, aliens, bullets):
	"""检查是否有外星人到达了屏幕底端"""
	screen_rect = screen.get_rect()
	for alien in aliens.sprites():
		if alien.rect.bottom >= screen_rect:
			# 像飞船被撞到一样进行处理
			ship_hit(ai_settings, stats, screen, ship, aliens, bullets)
			break

	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	
	